1. Field of the Invention
This invention relates to piston rods, particularly for hydraulic, hydro-pneumatic and pneumatic cylinder piston units, for example, oscillation dampers. A new method for manufacturing such a piston rod is proposed which is both very economic and warrants a very strong connection between the piston rod member itself and terminal parts to be fixed to the piston rod member.
2. The Prior Art
According to the most common methods known in the art the terminal members of piston rod units are fastened to tubular piston rod members by welding or soldering. These known techniques have the disadvantage that both the tubular piston rod member and the terminal members must consist of specific materials which allow excellent welding and soldering connections. Moreover by the high temperatures occurring during welding and soldering the members to be connected are frequently subject to thermal deformation.
From German Offenlegungsschrift 22 48 374 a piston rod unit is known in which a fastening pin of a terminal member is inserted into an end portion of the cavity defined within a tubular piston rod member. The fastening pin is provided with an annular groove on its outer circumferential face. The material of the piston rod member is deformed along the peripheral groove of the fastening pin so as to completely fill this peripheral groove. As a consequence of the deformation of the material of the tubular piston rod member a peripheral groove appears on the outer circumferential face of the tubular piston rod member such that the piston rod member does not provide a smooth cylindrical surface over its total length. In other words: The effective length of the piston rod member is reduced.